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Electronics is the study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The pure study of such devices is considered as a branch of physics, while the design and construction of electronic circuits to solve practical problems is called electronic engineering.

The main uses of electronic circuits are the controlling, processing and distribution of information, and the conversion and distribution of electrical power. Both of these uses involve the creation or detection of electromagnetic fields and electric currents.

While electricity had been used for some time to transmit data over telegraphs and telephones, the development of electronics truly began in earnest with the advent of radio. Today, electronic devices perform a much wider variety of tasks.

One way of looking at an electronic system is to divide it into the following parts:

  1. Inputs - Electrical or mechanical sensors (or transducers), which take signals (in the form of temperature, pressure, etc.) from the physical world and convert them into current/voltage signals.

  2. Signal processing circuits - These consist of electronic components connected together to manipulate, interpret and transform the signals.

  3. Outputs - Actuators or other devices (also transducers) that transform current/voltage signals back into useful physical form.

Take as an example a television. Its input is a broadcast signal received by an antenna or fed in through a cable. Signal processing circuits inside the television extract the brightness, colour and sound information from this signal. The output devices are a cathode ray tube that converts electronic signals into a visible image on a screen and magnet driven audio speakers.

Table of contents

Electronic Test Equipment

  • Ammeter, e.g. Galvanometer (Measure current)

  • Ohmmeter, e.g. Wheatstone bridge (Measure resistance)

  • Voltmeter (Measures voltage)

  • Multimeter (Measures all of the above)

  • Logic analyzer (Tests digital circuits)

  • Oscilloscope (Measures all of the above as they change over time)

  • Electrometer (Measures charge)

Interconnecting Electronic Components

  • electrical connectors, plugs and sockets etc.

  • printed circuit boards

  • integrated circuit

  • point-to-point construction

  • wire-wrap

  • breadboard

Passive Components

  • resistor

  • capacitor

  • inductor

  • transformer

  • piezoelectric crystal

  • magnetic amplifier (toroid)

Active Components (solid-state)

  • diode

    • light emitting diode

    • photodiode

    • laser diode

    • Zener diode

    • Schottky diode

    • transient voltage suppression diode

    • variable capacitance diode

  • transistor

    • field effect transistor

    • bipolar transistor

    • IGBT transistor

    • Darlington transistor

    • photo transistor

  • other active components

    • triac

    • thyristor

    • unijunction transistor

    • varistor

    • Silicon Controlled Rectifier (SCR)

Active Components (thermionic)

  • thermionic valve

  • cathode ray tube

  • klystron

  • magnetron

Electromechanical Sensors and Actuators

  • microphone

  • loudspeaker

  • strain gauge

  • switch

Thermoelectric devices

  • thermistor

  • thermocouple

  • thermopile

  • Peltier cooler

Photoelectric devices

  • light-dependent resistor

  • photodiode

  • photovoltaic cell (solar cell)

Antennae etc.

  • radio antenna

Analog circuits

Most analog electronic appliances, such as radio receivers, are constructed from arrays of a few types of circuits.

  • Analog computer

  • Analog multipliers

  • electronic amplifiers

  • electronic filters

  • electronic oscillators

  • electronic mixers

  • electronic power supply

  • impedance matchers

  • operational amplifiers

Digital circuits

Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. Digital Signal Processors are another example.

  • logic gates

  • flip-flops

  • counters

  • registers

  • multiplexers

  • microprocessors

  • microcontrollers

  • DSP

Mixed-signal circuits

Mixed-signal circuits, also known as hybrid circuits, are becoming increasingly common. Mixed circuits contain both analog and digital components. analog to digital converters and digital to analog converters are the primary examples. Other examples are transmission gates and buffers.


Associated with all electronic circuits is noise. Types of noise include

  • Shot noise in resistors.

  • Thermal noise in resistors.

  • White noise

  • Coloured noise

Electronics Theory

  • Mathematical Methods of Electronics

  • Digital Electronics

  • Analog Electronics

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